Vehicles today are required to meet strict emission requirements, and consequently require catalytic converters and advanced engine controls to minimize any potentially harmful emissions flowing from the exhaust created by an internal combustion engine. In order to control the engine and monitor its performance, on-board gas sensors are used to continuously monitor the exhaust gases as they flow from the engine. Sensors employed for this use must withstand the greatly varying temperatures, different gases to which the sensor is exposed, vibration, moisture, etc., as is generally created in an environment around a vehicle engine. Therefore, maintaining the integrity and accuracy of the sensor is difficult over long periods of time. Further, the size and weight requirements for the sensor may be limited due to limitations on the vehicle.
U.S. Pat. No. 5,490,490 to Weber et al., incorporated herein by reference, describes an on-board gas composition sensor for analyzing internal combustion engine exhaust gases. The device employs a light source that excites a fluorescence in an inorganic-oxide ceramic sensor body exposed to gases in the engine exhaust stream. The intensity of that fluorescence is related to either the oxygen concentration or reductant to oxidant ratio of the exhaust gas. While this sensor works well for this purpose, a smaller, and lighter assembly is desirable due to the continued emphasis on lighter and smaller vehicles in order to improve fuel economy. Also, it is desirable to have a more robust sensor that assures proper alignment and operation of the sensor assembly components for the life of the sensor, assuring better reliability. Further, it is desirable to have a more cost effective way to implement this type of sensor.